1. Field of the Invention
The present invention relates to a method of manufacturing a battery (nonaqueous secondary battery) including a nonaqueous electrolytic solution.
2. Description of Related Art
During the manufacture of a nonaqueous secondary battery such as a lithium ion secondary battery, for example, a battery assembly is constructed using a positive electrode, a negative electrode, and a nonaqueous electrolytic solution. Next, this battery assembly undergoes treatments such as initial charging (conditioning), keeping at a high temperature range (aging), and quality inspection. For example, Japanese Patent Application Publication No. 2005-251538 (JP 2005-251538 A) discloses a self-discharge test method of a secondary battery, the method including: charging a constructed battery assembly to a predetermined voltage; leaving the battery assembly to stand for a predetermined period; and determining whether internal short-circuit occurs based on a voltage change amount between voltage values before and after the standing (voltage drop amount).
However, in a nonaqueous secondary battery, a nonaqueous electrolytic solution may contain additives to improve durability. For example, when a so-called film forming agent (for example, an unsaturated carbonate) is added during the construction of a battery assembly, the compound is decomposed, typically, during initial charging to form a film (protective film) on a surface of an electrode (for example, a negative electrode). This film stabilizes an interface between the electrode and the nonaqueous electrolytic solution and improves the durability (for example, cycle characteristics or high-temperature storage characteristics) of the battery. However, according to a new finding obtained by the present inventors, when a nonaqueous electrolytic solution contains an unsaturated carbonate, the above-described self-discharge test may be delayed. Accordingly, from the viewpoints of productivity, working efficiency, and cost, it is required to reduce a self-discharge test period without decreasing test accuracy even when a nonaqueous electrolytic solution contains the unsaturated carbonate.